In recent years, an axial-type rotary electric machine has been paid attention. The present axial-type rotary electric machine has a structure in which a disc-shaped rotor and a stator are arranged so as to face each other, and the structure is advantageous for achieving a thin and flat rotary electric machine. Also, the present axial-type rotary electric machine can be configured as a double-rotor type having a stator sandwiched by two rotors in an axial direction. A general double-rotor type rotary electric machine has a configuration in which a plurality of independent cores each wound with a winding wire is circumferentially arranged and which is provided with a stator molded with a resin and a rotor obtained by connecting a yoke to a plurality of circumferentially-arranged permanent magnets. A torque of a motor is proportional to a gap area which is a facing surface between the rotor and the stator, and the double-rotor type rotary electric machine allows increase in the gap area per body, and therefore, is effective for achieving high output power and high efficiency. Further, the inventors consider that the double-rotor type is an effective structure for application to an amorphous metal having a feature of low loss. Because of hard and fragile, the amorphous metal is difficult to be processed. In the double-rotor type rotary electric machine, a core can be configured with an extremely simple shape such as a substantially rectangular parallelepiped shape by preparing the stator core as an open slot. Therefore, the amorphous metal can be processed into a core shape by a simple method.
In order to improve the torque and efficiency of the axial-type rotary electric machine, it is effective to expand its diameter to increase an area (hereinafter “gap area”) at which the stator and the rotor face to each other. However, this manner requires a caution because a centrifugal force acting on the rotor increases. Particularly, since the axial-type rotary electric machine has a surface-magnet configuration in which a permanent magnet is arranged on a surface of the rotor in many cases, the axial-type rotary electric machine has a problem of scattering and a breakage of the magnet due to the centrifugal force.
A prior art example of the rotor structure of the axial-type rotary electric machine will be described below.
A rotor described in Patent Documents 1 and 2 is configured by a permanent magnet, a yoke, and a support member used for supporting them and fixing them to a shaft. A protrusion which covers the outer peripheral surface of the permanent magnet is provided on the outer diameter side of the support member so as to improve strength against the centrifugal force. Such a rotor structure is commonly observed even in other inventions related to the axial-type rotary electric machine.